Tissue reaction, that is caused when polymeric materials are implanted in living tissue, is generally studied histopathologically. The histopathological evaluation is time-consuming as a first step to make an assessment of new polymeric materials. Considering that tissue reaction is usually caused by the presence of low molecular weight compounds such as various additives, monomers, impurities and degradation products of polymers, elution, hemolysis and enzymatic degradation tests were performed in vitro. And in vitro results are compared with those obtained in vivo histopathologically. Test materials were extracted in distilled water, the eluates analyzed spectrophotometrically, elution rate of leaching substances was determined and it gives a criterion of degree of tissue reaction. The repeated extraction test gave an information as to the duration or pattern of tissue reaction. The materials tested are silicone rubber, polyurethane, thermoelastic rubber, polysulfone, polyethylene carbonate. The in vitro evaluation methods studied here provided an useful information to understand the intensity, pattern or duration of tissue reaction.
In order to test the utility as a biomedical material, we prepared the film shaped polyethylene-collagen (proteinase treated bovine collagen) and polyvinyl-alcohol-collagen grafted copolymers using Okamura and Hino's method (namely, polymerization achieved by the introduction of cross-linkages, applying electricity aid irradiation). We examined the tissue affinity of these copolymers whether copolymers are joined with the tissue. These films were implanted subcutaneously in rabbits and removed with the surrounding tissues after 1, 2, 3, 4 and 6 weeks to be examined with microscope and scanning electron microscope. One week after implantation, we observed that a large number of fibroblasts gathered on the surface of the grafted collagen. After three or four weeks, bridges of collagenfibrils were observed between the copolymer and rabbit tissue. These films were firmly adhered with surrounding tissues and were separable only with difficulty. These results suggest that the plastics, grafted bovine collagen and rabbit collagen are combined to form ultramacromolecules; also, collagen plastics copolymers have very efficient affinity for tissue. From these experimental results we concluded that collagen plastics copolymers are useful as a biomedical material.
As pacemaker check system via telephone, we started the experiment in September 1973, considering acoustic coupling transmission and direct wired coupling receiving. Making sure of its effectiveness, we went to business in October 1974. Acoustic coupling transmission has two methods, two channel (ECG, PMP) and one channel (ECG). Output of tansmitter is limited below 0.9Nm2/wave, therefore two channel method it must be 0.4Nm2/wave. Sixty% of patient cases, is impossible to transmit by two channel method. In one channel method (0.9Nm2/wave), one case of 60 cases was impossible, all of others possible.
Twelve patients who had been implanted artificial pacemaker for the treatment of bradycardia due to atrioventricular block, S.S.S. and atrial fibrillation were studied to determine the respone to digitalis in the resting position using mechanocardiogram. The ejection time, isometric contraction time, preejection period and Q-SII interval shortened following digitalis administration. There was not found significant relationship between the changes in ejection time and preejection period. The degree of shortening of ejection time was more remarkable in the elder patient and/or with diastolic hypertension, while the degree of shortening of preejection period was more remarkable in the catient with S.S.S and atrial fibrillation and/or normotension. It is considered that the results obtained in this study were produced by complicated consequences including an increased force and velocity of the cardiac contraction, increased peripheral arterial resistance and increased cardiac output due to digitalis, and probably underlying disease.
The characterestics of the circulatory autoregulation during artificial heart pumping were studied, employing a simple mathematical model of the pulmonary and systemic circulation and the artificial heart. The unstable physiological state of arterial and venous pressure caused by the decreased cardiac output sensitivity to the venous pressure and the elevation of the pulmonary venous pressure more than 10 mmHg caused by the of terload effects, i.e., the decreases in cardiac output with increased arterial pressure, were predicted by numerical computations under the case of left, right or total artificial heart replacement. To improve the characterestics of the circulatory autoregulation, the servo-mechanism control and driving system of the total artificial heart was designed. In this system, cardiac output was regulated by the automatic changes in the driving pressure corresponding to the changes in the venous pressure, so that the venous pressure could be maintained at any constant level or within any desired range during the pumping.
Various kinds of circuit systems for cardiopulmonary bypass using a membrane oxygenator have been considered. The author considered comparing three types of circuit simultaneously using a switch circuit when two membrane oxygenators were used, and found that a new type circuit, which contains one oxygenator (low flowresistance oxygenator only) in a gravity drainage line and one oxygenator (high flow-resistance oxygenator also available) in a recirculation line, had a great advantage of stable oxygenation and an easy control of the oxygenation level within the desired value with a flow rate control of a recirculation pump. For the purpose of clinical application, we have improved a hard shell reservoir which is convenient for this circuit system, controlled oxygenation circuit system. The reservoir is separated by a septum located in the center, of which the sides are jagged, so that blood communication between the two chambers is possible. Both chambers are open to the atmosphere, so air bubbles are easily trapped. Twenty infants and children underwent cardiopulmonary bypass using this controlled oxygenation circuit system. Among them, 5 patients with transposition of the great arteries and two patients of total anomalous PV drainage were operated upon using the technique of surface cooling and limited cardiopulmonary bypass. Remaining 13 cases of VSD with pulmonary hypertension and others were operated upon under total cardiopulmonary bypass. The results were satisfactory. The patient's ages, body weight, hematocrit value, plasma sodium concentration, and plasma free hemoglobin and also blood gas data were shown.
Twenty-one patients of chronic renal failure with congenital and aquired heart diseases have been treated with long-term peritoneal dialysis. Hemodynamical effect of peritoneal and hemodialysis on the patients of chronic renal failure examined by mechanocardiography. The results of mechanocardiogram recorded during peritoneal dialysis suggest that the dialysis does not introduce hemodynamical load on the heart of the patient. The results of mechanocardiograms from the same patient recorded during peritoneal and hemo-dialysis respectively suggest that hemodynamical load on the heart by peritonea ldialysis is much less than that of hemodialysis in following reasons; 1. Cardiac output increases in both peritoneal and hemo-dialysis, but increment of it is bigger in peritoneal dialysiss than hemodialysis. 2. Ejection time index decreases in hemodialysis. 3. Isometric contraction time decreases in peritoneal dialysis but increases in hemodialysis. 4. Ejection time and pre-ejection period ratio is much decreased in hemodialysis than peritoneal dialysis, and decrease of myocardial contractility might exist during hemodialysis. Furthermore, since middle molecular weight substances are well dialysed by peritoneal dialysis rather than hemodialysis, peritoneal dialysis might be suitable treatment for uremic patients with heart diseases. Survival rate of the patients treated by long-term peritoneal dialysis is not statistically different from that of the patients treated with hemodialysis aged between 41 to 65 (mean±1 S. D. of age of peritoneal dialysed patients). Tenckhoff chronic catheter was used in all cases and this catheter seems to be the best one for currying the long-term peritoneal dialysis.